Several different types of indicators or sensors for monitoring the wear of the brake lining of a brake pad or the like are known. In principle the known sensors operate in two different ways for monitoring wear of brake linings. The first way is to use a sensor that measures directly on the brake lining. The second way is to use a sensor that monitors the position or movement of a part indicative of the wear of the brake linings. The present invention concerns a sensor element monitoring the position of a part, indicative of the wear of the brake linings. It should be noted that in the latter case also the wear of the brake disc(s) and possible lining material of the brake disc(s) are included in the sensed wear. However, the wear of the brake disc(s) as such is normally negligible compared to the wear of the lining material. For simplicity of this description the wear is normally stated in reference to the brake lining material, which is the normal usage in the art. Thus, it is to be understood that also the wear of the disc(s) is included in general expressions regarding wear in this description.
Disc brakes are generally of two different types, which are referred to as disc brakes having a fixed caliper or a floating caliper. The present invention is applicable for both the above types of disc brakes.
The sensor system according to the present invention is normally to be applied in connection with an adjustment shaft. The adjustment shaft is a part of an adjustment mechanism, used to control the position of the brake pads in relation to the brake disc(s), as is well known in the art. As the lining of the brake pads wear off, the position of the brake pads in relation to the brake disc(s) is automatically adjusted, by means of the adjustment mechanism. Hereby the distance between the lining material and the brake disc(s) is kept more or less constant. The amount of rotation of the adjustment shaft or adjusting spindle is correlated to the distance the adjuster mechanism advances the brake pads towards the brake disc(s). Thus, the rotation of the adjustment shaft is an indicator of the wear of the brake pads of the disc brake.
When worn brake pads are to be replaced by new brake pads, the adjustment mechanism, and thus, the adjustment shaft, is brought back to a starting position. This is done to give room for the new thicker brake pads. The starting position is dependent on the thickness of the brake disc(s) and is due to the wear of the disc(s). Thus, the starting point could be used to monitor the wear of the brake disc(s).